1. Field of Use
This invention relates generally to components, such as splices, elbows or terminators, which are used for splicing or terminating electric cables used in high voltage electrical power transmission and distribution systems.
In particular it relates to heat transfer devices for transferring heat from a cable connector located within an insulating housing in such a component to the housing for dissipation therefrom to atmosphere.
2. Description of the Prior Art
High voltage electrical systems of the aforesaid character employ relatively large cables which need to be spliced together end-to-end or need to have a cable end connected to a terminal on electrical apparatus such as a transformer, circuit breaker or the like. The cable typically comprises an electrical conductor (usually formed of multiple strands of wire), an electrical insulating sheath surrounding the electrical conductor, a semi-conductor sheath surrounding the insulation, and electrical shielding (usually formed by woven wire) surrounding the insulating sheath. Cable splicing or cable termination requires use of a component, such as a splice or elbow or terminator, which can withstand high voltage and high temperature and is mechanically strong.
Such a high voltage component typically comprises an electrically insulating housing having a connector cavity therein which is accessible through at least one cable-receiving passage extending into the housing. The cavity is defined or surrounded by an electrically conductive hollow stress relief insert closely connected as by bonding to the insulating material of which the housing is made. In a finished installation a metal electrical connector is located within the stress relief insert and the end of a cable extends through a cable-receiving passage into the hollow stress relief insert and the stripped conductor is electrically and mechanically joined to the electrical connector as by crimping. In a splicing component the ends of two cables extend into the housing and are joined end-to-end to the connector. In an elbow or terminator the end of only one cable extends into the housing and is joined to the connector which has a terminal attached thereto. In operation, electrical current flow through the electrical connector (which can range from 20 to up to 600 amperes, depending on the size of the system) can cause relatively high temperatures at the connector and in the housing cavity due to the electrical resistance in the connector joint. Such heating can cause or accelerate deterioration (i.e., "aging") of the dielectric and nondielectric organic materials of which the housing and cable insulation are made and can create a risk of mechanical failure, electrical breakdown or flashover and even fire.
The prior art discloses various means and measures which can be employed to dissipate the heat from the connector and the housing cavity. Thus, in some components, for example, the stress relief insert in the housing cavity is constructed with one or more integrally formed inwardly extending flexible projections which physically engage the connector and transfer heat therefrom to the housing for dissipation to atmosphere. U.S. Pat. No. 4,079,189 discloses a component, such as a cable splice, employing such a stress relief insert. However, such projections can make it difficult to slip the cable(s) and the attached connector through the housing passage into the hollow stress relief insert defining the cavity after splicing is accomplished. Another approach is to make the housing of sufficiently large mass relative to expected temperatures so as to enable the housing to absorb and dissipate connector and cavity heat rapidly enough to keep temperatures low and minimize deterioration. However, this can result in unduly large and costly housings. Still another approach is shown in U.S. Pat. No. 3,691,291 wherein a metal connector is provided with metal collars which are threadedly mounted thereon and which engage the stress relief insert surrounding the connector cavity to transfer heat to the housing for dissipation. The metal collars enlarge the surface contact area between the connector and cavity wall. However, this component may be difficult and time consuming to assemble, is rigid and is relatively costly.